Interpretive Summary: Taenia talicei is redescribed based on new data for polycephalic, fimbriocercus and cysticercus metacestodes in Ctenomys spp. (Rodentia: Ctenomyidae) from Argentina. Strobilate adult specimens derived from experimental infections in domestic dogs are morphologically characterized for the first time. Unequivocal identity for adults and metacestodes is established based on the number (44-50 hooks in 2 rows), dimensions (large hooks= 232-242 'm; small= 150-187) and structure of rostellar hooks. Taenia talicei is distinguished from those species that naturally occur in Neotropical Felidae and from those cosmopolitan species that circulate in synanthropic cycles with rodents (or lagomorphs) and domestic hosts such as cats and dogs in South America based on the structure of the metacestode, dimensions and numbers of rostellar hooks and a suite of specific characters of the genital system in strobilate adults. Taenia talicei is the first described species that can be considered endemic from South America. Origins of an endemic Taenia or assemblage of Taenia-species in South America would have relationships to either North America or directly to Eurasia and placental carnivores. In these instances the expansion of Taenia may have resulted from geographic colonization of South America, radiation of both felids (and canids), and host switching by tapeworms to caviomorphs, prior to the emergence of the Panamanian Isthmus. Taenia talicei is capable of development in domestic dogs, and metacestodes in species of Ctenomys were found in urban or semi-urban environments. These factors may establish the role for synanthropic cycles linked to definitive hosts including dogs and cats as a route for exposure of humans to infection by this taeniid.

Technical Abstract:
Taeniid tapeworms are characteristic parasites in both domesticated and wild carnivores and life cycles are completed through predator-prey associations with rodent, lagomorph or ungulate intermediate hosts that harbor infective larvae. Globally these tapeworms contribute to morbidity and mortality in both domestic and free-ranging hosts, and can pose a risk for human infection as zoonoses (parasites transmissible from animal to man). We continue to reveal new information about the host and geographic distribution of species of Taenia tapeworms and such provides a foundation for identifying and documenting the risk for human infection on global to local scales. These parasites are the most poorly known in South America, and we have now characterized the endemic species, Taenia talicei for the first time; the species was previsouly only klnown from larvae in rodents. Taenia talicei is redescribed based on new data for polycephalic, fimbriocercus and cysticercus metacestodes in Ctenomys spp. (Rodentia: Ctenomyidae) from Argentina. Adult specimens derived from experimental infections in domestic dogs are morphologically characterized for the first time. Unequivocal identity for adults and metacestodes is established based on the number (44-50 hooks in 2 rows), dimensions (large hooks= 232-242 'm; small= 150-187) and structure of rostellar hooks. Taenia talicei is distinguished from those species that naturally occur in Neotropical Felidae and from those cosmopolitan species that circulate in synanthropic cycles with rodents (or lagomorphs) and domestic hosts such as cats and dogs in South America based on the structure of the metacestode, dimensions and numbers of rostellar hooks and a suite of specific characters of the genital system in strobilate adults. Taenia talicei is the first described species that can be considered endemic from South America. Origins of an endemic Taenia or assemblage of Taenia-species in South America would have relationships to either North America or directly to Eurasia and placental carnivores. In these instances the expansion of Taenia may have resulted from geographic colonization of South America, radiation of both felids (and canids), and host switching by tapeworms to caviomorphs, prior to the emergence of the Panamanian Isthmus. Taenia talicei is capable of development in domestic dogs, and metacestodes in species of Ctenomys were found in urban or semi-urban environments. These factors may establish the role for synanthropic cycles linked to definitive hosts including dogs and cats as a route for exposure of humans to infection by this taeniid. Charactertization of biodiversity is a fundamental step in understanding the distribution of pathogens and the potential for disease. Our study of T. talicei contributes to a growing foundation of data for the biology of Taenia species throughout the world.